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Publication - Professor Michael Kendall

    Measuring changes in fracture properties from temporal variations in anisotropic attenuation of microseismic waveforms

    Citation

    Usher, P, Kendall, JM, Kelly, CM & Rietbrock, A, 2017, ‘Measuring changes in fracture properties from temporal variations in anisotropic attenuation of microseismic waveforms’. Geophysical Prospecting.

    Abstract

    We investigate fracture-induced attenuation anisotropy in a cluster of
    events from a microseismic dataset acquired during hydraulic fracture
    stimulation. The dataset contains 888 events of magnitude −3.0 to 0.0.
    We use a log-spectral-amplitude-ratio method to estimate change in
    over a half-hour time period where fluid is being injected and an
    increase in fracturing from S-wave splitting analysis has been
    previously inferred. A Pearson's correlation analysis is used to assess
    whether or not changes in attenuation with time are statistically
    significant. P-waves show no systematic change in
    during this time. In contrast, S-waves polarised perpendicular to the
    fractures show a clear and statistically significant increase with time,
    whereas S-waves polarised parallel to the fractures show a weak
    negative trend. We also compare between the two S-waves, finding an increase in
    with time. A poroelastic rock physics model of fracture-induced
    attenuation anisotropy is used to interpret the results. This model
    suggests that the observed changes in t* are related to an increase in
    fracture density of up to 0.04. This is much higher than previous
    estimates of 0.025 ± 0.002 based on S-wave velocity anisotropy, but
    there is considerably more scatter in the attenuation measurements. This
    could be due to the added sensitivity of attenuation measurement to
    non-aligned fractures, fracture shape, and fluid properties.
    Nevertheless, this pilot study shows that attenuation measurements are
    sensitive to fracture properties such as fracture density and aspect
    ratio.

    Full details in the University publications repository